Now, this self-evident knowledge may be assailed by doubts and whisperings, such as sophistical objections raised against sensory and self-evident knowledge. These include the objections al-Rāzī presented at the beginning of his Muhassal, which we have discussed elsewhere.

Objections that undermine this knowledge cannot be answered by rational demonstration, because demonstration must ultimately rest upon it. Once this knowledge is called into doubt, the path of rational inquiry and investigation is cut off.

For this reason, someone who denies sensory and self-evident knowledge is not engaged in debate. Rather, if he stubbornly rejects the truth, he is punished until he acknowledges it. If, however, he is mistaken because an impairment has affected his senses or intellect, leaving him unable to grasp this knowledge, or for some similar reason, he is treated by means that establish the conditions necessary for knowledge and remove its impediments. If a defect in his constitution prevents this, he is treated with physical medicines, or with supplication, healing recitations, devotional turning, and the like. Otherwise, he is left alone.

Hence, rational people agree that not every doubt that arises can be dispelled through demonstration, inquiry, and inference. These methods can be addressed only to someone who possesses known premises and is capable of examining them in a way that yields further knowledge. Someone who lacks known premises or is incapable of examining them cannot be addressed through rational inquiry and inference.